The present invention relates to an exhaust heat exchanger with catalyst in which an exhaust gas purification apparatus (a catalytic converter) utilizing a catalyst for using in an exhaust system of an internal combustion engine is combined with a heat exchanger for recovering heat of the exhaust gas to make the exhaust system compact and improve silencer effect and heat exchanger performance.
Heretofore, the exhaust system in this kind of internal combustion engine has been constituted as shown in FIG. 4.
Namely, in FIG. 4, an exhaust gas discharged from an internal combustion engine 01 firstly enters an exhaust gas purification apparatus (a catalytic converter) 02 where injurious components in the exhaust gas are purified, and then the exhaust gas is discharged from the converter.
Then, the purified and somewhat warmed exhaust gas enters a heat exchanger 03 where the exhaust gas makes a heat exchange with a cooling water of the internal combustion engine and gives its heat to the cooling water, and the exhaust gas itself which has been cooled is discharged is discharged from the heat exchanger.
The cooling water entering the heat exchanger 03 has been sufficiently cooled by making a heat exchange with a cold water such as city water in a heat exchanger 04 for recovering exhaust heat which the cooling water passes through after it comes out of the internal combustion engine 01. Therefore, the purified and somewhat warmed exhaust gas can be cooled effectively. Though the cooling water is somewhat warmed by the heat exchange, it is returned to the engine 01 and cools various parts of the engine 01 without difficulty.
The city water warmed by the heat exchange with the cooling water in the heat exchanger 04 is directed to a hot-water supply facility, an air conditioning facility, or the like, of a place of business or a home to be used as hot-water directly or as heat source of hot-water.
As mentioned above, in the exhaust system of the conventional internal combustion engine 01, the exhaust gas purification apparatus 02 is disposed on an upper stream side of an exhaust gas passage and formed separately from the heat exchanger 03. Therefore, a space is required for constituting the exhaust system, moreover, construction of the system is complicated.
The present invention aims to solve the aforementioned problems of the exhaust system in the conventional internal combustion engine 01, and provide an exhaust heat exchanger with catalyst in which the exhaust system is made compact, the construction is simplified, the manufacturing cost is reduced and silencer effect and heat exchange performance can be improved.
The present invention provides an exhaust heat exchanger with catalyst, comprising a water chamber which a cooling water flows through and a catalyst chamber housing a catalyst which an exhaust gas flows through in contact with the catalyst, thereby the exhaust gas coming out of the catalyst chamber makes an indirect heat exchange with the cooling water before the exhaust gas is discharged outside.
In this invention, the catalyst chamber corresponding to an exhaust gas purification apparatus (a catalytic converter) used in a exhaust system of an internal combustion engine is provided within the water chamber and the exhaust gas having passed through the catalyst chamber makes an indirect heat exchange with the cooling water in the water chamber, thus the exhaust purification apparatus is integrally combined with a heat exchanger for recovering heat of the exhaust gas.
As the result, the exhaust system of the internal combustion engine can be made compact and simplified in construction and the manufacturing cost thereof can be reduced.
Since the catalyst chamber is surrounded by the water chamber, heat possessed by the exhaust gas and reaction heat between the exhaust gas and the catalyst are absorbed by the cooling water in the water chamber sufficiently to improve heat exchange performance.
Though the exhaust system is made compact by combining a exhaust purification apparatus and a heat exchanger for recovering heat of exhaust gas integrally as a unit, capacity of the whole unit is larger than that of the conventional individual exhaust gas purification apparatus or heat exchanger for recovering heat of exhaust gas. Therefore, noise generated by the exhaust gas is damped when the exhaust gas flows through a chamber of large capacity. The damping of the noise is further enhanced by the water chamber surrounding the chamber of large capacity so as to confine it. Thus, an improved silencer effect can be obtained.
The water chamber may be formed between an inner trunk and an outer trunk, the catalyst chamber may be formed by a cylindrical body disposed coaxially with the inner and outer trunks, the catalyst may be disposed within the cylindrical body, a spiral passage for the exhaust gas may be formed between the inner trunk and the cylindrical body, and a plurality of heat transmission pipes may be arranged surrounding the inner trunk circumferentially at regular intervals, thereby the exhaust gas flows within the catalyst, flows into the spiral passage, then flows within the heat transmission pipes to make a heat exchange with the cooling water.
As the result, the exhaust heat exchanger with catalyst presents a whole appearance of a columnar shape, because the outer trunk, the heat transmission pipes, the inner trunk, the spiral passage, the cylindrical body (catalyst chamber) and the catalyst are disposed concentrically. Therefore, the heat exchanger can be made further compact, the construction can be simplified and the manufacturing cost can be reduced.
Since the exhaust gas flows passing through the catalyst, the spiral passage and the heat transmission pipes in the water chamber in turn, a sufficient heat exchanging area is ensured by the inner trunk and the heat transmission pipes, and the exhaust gas makes a sufficient heat exchange with the cooling water to improve heat exchange performance.
The cylindrical body may be surrounded by a heat shielding cylindrical body with a thin adiabatic gas layer lying between.
Since the adiabatic gas layer lies between the spiral passage and the catalyst, and a hot exhaust gas having just passed through the catalyst enters the adiabatic gas layer from a bottom of the layer, temperature of the exhaust gas in the spiral passage is hardly transmitted to the catalyst, and even if the exhaust gas in the spiral passage is cooled by the cooling water in the water chamber, lowering of temperature of the catalyst can be prevented, so that purification of injurious components in the exhaust gas is promoted to improve exhaust gas purification performance.
Because the hot exhaust gas enters the adiabatic gas layer on outside of the catalyst, a time required for activating the catalyst after the engine is started is shortened to promote purification of injurious components in the exhaust gas, and the exhaust purification performance is improved also in this aspect.